Reversing Coffee-Ring Effect by Laser-Induced Differential Evaporation

Abstract

The coffee-ring effect, ubiquitously present in the drying process of aqueous droplets, impedes the performance of a myriad of applications involving precipitation of particle suspensions in evaporating liquids on solid surfaces, such as liquid biopsy combinational analysis, microarray fabrication, and ink-jet printing, to name a few. We invented the methodology of laser-induced differential evaporation to remove the coffee-ring effect. Without any additives to the liquid or any morphology modifications of the solid surface the liquid rests on, we have eliminated the coffee-ring effect by engineering the liquid evaporation profile with a CO2 laser irradiating the apex of the droplets. The method of laser-induced differential evaporation transitions particle deposition patterns from coffee-ring patterns to central-peak patterns, bringing all particles (e.g. fluorescent double strand DNAs) in the droplet to a designated area of 100 μm diameter without leaving any stains outside. The technique also moves the drying process from the constant contact radius (CCR) mode to the constant contact angle (CCA) mode. Physical mechanisms of this method were experimentally studied by internal flow tracking and surface evaporation flux mapping, and theoretically investigated by development of an analytical model.

Adsorption of nanoparticles suspended in a drop on a leaf surface of Perilla frutescens and their infiltration through stomatal pathway

“…2 e). To reduce the thermal effect of laser on drop evaporation, laser was irradiated at low light intensity 40 . Polystyrene particles (PSP) of 1 µm in diameter were selected as tracing fluorescent particles to ensure the similar theoretical v sed value with those of AuNPs and ultrafine A1 dust particles.…”

Nonuniform heating of a substrate in evaporative lithography

“…In addition, it accelerates the drying process and the formation of a hard coating. The effect of laser heating of the droplet apex on the deposition structure of colloidal particles was compared with heating of the entire substrate in [12]. A similar experiment was performed with a drop of saline solution on hydrophobic and hydrophilic substrates [13].…”

Specific Features of Crystallization Process of 4,4'-Azoxyanisole in the Form of Multiple «Coffee Rings»

“…Например, воздействуя на каплю ультразвуком в процессе ее высыхания можно добиться исчезновения эффекта «кофейного кольца» [9]. В ряде работ используется электросмачивание [10,11] или лазерное излучение [12] для равномерного нанесения покрытия на подложку. В работе [13] исследовано влияние поверхностно-активных веществ на форму «кофейного кольца».…”